I get the feeling that when most people use the term "ki", they don't mean what you mean...

I don't doubt it. Francis Takahashi has a blog post on Aikido Journal here that says in part: "In Japanese, the word "Ki" has many meanings, dependent on the intent or purpose of the user. By itself, it has little or no utility or significance. It is when it is used with other words that the true intent of its use is revealed." That nicely sums up my position on the "What is Ki?" question. I don't worry about what it is but, based on my working definition, I know it when I feel it.